不能用剑柄，Android注入房刀

Question

我正在尝试使用 Hilt 将房间 DAO 注入存储库。我正在使用以下代码：

def room_version = "2.2.6"
ext.hilt_version = '2.33-beta'

implementation "androidx.room:room-runtime:$room_version"
kapt "androidx.room:room-compiler:$room_version"
implementation "androidx.room:room-ktx:$room_version"
implementation "androidx.room:room-guava:$room_version"
testImplementation "androidx.room:room-testing:$room_version"

implementation "com.google.dagger:hilt-android:$hilt_version"
kapt "com.google.dagger:hilt-compiler:$hilt_version"

刀

@Dao
interface SearchDAO {

    @Query("SELECT * FROM searches_table WHERE name LIKE '%' || :query || '%'")
    fun readSearches(query : String) : Flow<List<SearchItem>>

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insertSearch(search : SearchItem)

    @Delete
    suspend fun deleteSearch(search: SearchItem)
}

数据库

@Database(
        entities = [SearchItem::class],
        version = 1
)
abstract class SearchesDatabase : RoomDatabase(){
    abstract fun getSearchesDao() : SearchDAO
}

供应商

@Module
@InstallIn(ActivityComponent::class)
object AppModule{
    @Singleton
    @Provides
    fun provideSearchDatabase(@ApplicationContext context : Context) =
        Room.databaseBuilder(context, SearchesDatabase::class.java, SEARCH_DATABASE_NAME)
            .fallbackToDestructiveMigration()
            .build()

    @Provides
    fun provideSearchDAO(appDatabase: SearchesDatabase): SearchDAO {
        return appDatabase.getSearchesDao()
    }
}

基础应用程序

@HiltAndroidApp
class BaseApplication : Application() {

    override fun onCreate() {
        super.onCreate()
        //Timber.plant(Timber.DebugTree())
    }
}

存储库注入

class Repository @Inject constructor(
    val searchesDao : SearchDAO
){
...
}

问题是我收到以下错误：

[Dagger/MissingBinding]com.example.leagueapp.database。如果没有@Provides注释方法，则无法提供SearchDAO。公共抽象静态类SingletoC实现BaseApplication_GeneratedInjector

Answer 1

请在应用模块类中编写以下代码。您只需要在@installIn（）注释中编写SingletonComponent:：class而不是ActivityComponent:：类即可

@Module
@InstallIn(SingletonComponent::class)
object AppModule{
    @Singleton
    @Provides
    fun provideSearchDatabase(@ApplicationContext context : Context) =
        Room.databaseBuilder(context, SearchesDatabase::class.java, SEARCH_DATABASE_NAME)
            .fallbackToDestructiveMigration()
            .build()

    @Provides
    fun provideSearchDAO(appDatabase: SearchesDatabase): SearchDAO {
        return appDatabase.getSearchesDao()
    }
}

Answer 2

简短的回答：任何@Singleton都必须安装在单例组件中。

解释：单例应该在他们所处的过程中生存。您的数据库是一个单例（可能应该是），但您正在使用 @InstallIn（ActivityComponent：：class），它告诉 dagger 此模块中提供的所有内容都应限定为活动的生命周期;当活动死亡时，模块将死亡。